<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      html,
      body,
      #app {
        margin: 0;
        padding: 0;
      }

      #app {
        display: flex;
        flex-direction: row;
        flex-wrap: wrap;
        justify-content: space-between;
      }

      button {
        margin-bottom: 10px;
        width: 50px;
      }
    </style>
  </head>
  <body>
    <div id="app">
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
      <button>A</button>
    </div>
  </body>
</html>
